The objective of the research is to elucidate the roles that antibody may play in tumor rejection. In one system of antibody dependent cell-mediated cytotoxicity using TNP-CRBC as target cells we will determine which subclasses of mouse anti-TNP are capable of inducing normal mouse spleen cells to become cytotoxic to the target cells. We will attempt to extend our studies of subclass specificity to a system involving a dividing target cell, the B16 melanoma. We intend to study factors which "block" tumor immunity in vitro with emphasis on establishing whether these factors are at least in part, antibody; if antibody is involved in "blocking", we will investigate the subclass specificity. The B16 melanoma in its syngeneic host will be tested for its ability to function as a model for a "blocking" system.